1. Field of the Invention
This invention is related to the interconnection of optical fiber cables, both in the form of fiber optic splices and to the interconnection of optical fiber cables to active optoelectronic devices. More specifically this invention is related to the interconnection of multiple fiber optic cables in a single multiposition connector in which each fiber can be precisely aligned with its corresponding optical element. This invention is also related to a device and method for providing sufficiently precise alignment in a multiposition connector which uses molded plastic components exhibiting the tolerances and dimensional irregularities consistent with conventional injection molding. This invention is also related to the interconnection of plastic optical fiber cables.
2. Description of the Prior Art
Fiber optic cables are typically employed in providing communications in a number of applications. One widespread use of these cable is in networking and telecommunications applications. Fiber optic cables are also seen as having advantages for use in signalling applications for products such as automobiles. Residential applications for fiber optics are also under consideration.
However, no matter what the intended application, the interconnection of optical fibers and coupling of active optoelectronic devices to optical fibers still require a degree of precision which is not required for conventional electrical connections. There are a number of fiber optic connectors which have been commonly and successfully employed for connecting one or two optical fibers and dual optical fiber cables are commonly used in networking applications. In general, however, most of these connectors require special tools, the use of epoxy and in some cases polishing operations for each of the fiber interconnections. These special assembly operations are required to prevent excessive losses at the interconnection . Proper alignment of the fibers is one requirement for minimizing such connection losses.
Both glass and plastic fiber optic cables are conventionally used and each is suited for specific applications. In general plastic fiber cable exhibits greater losses than glass fiber cables and precise alignment and a good end finish are necessary for both plastic and glass fibers. One method of terminating plastic fiber optical cables which has been successfully employed is to position the cable in a ferrule after removing a portion of the plastic optical fiber cable jacket from the end of the cable. The ferrule is precisely dimensioned to closely receive the stripped end of the cable and the cable end can be cut, polished or otherwise finished to provide a surface suitable for interconnection with low or at least acceptable losses. One technique for securing the fiber optical cable to the ferrule is to use a retainer which engages the outer jacket to hold the cable in place in the ferrule. One such retainer which has been employed is the use of a slotted plate member which is inserted into a laterally open cavity into the ferrule. The slots in the retainer plate engage the outer jacket of the fiber, but do not engage the underlying optical fiber. The fiber is thus mechanically held in the ferrule and suitable cleaving and finishing operations can be performed after the cable has been secured in the ferrule. A fiber optic connector employing these principles is shown in U.S. Pat. No. 4,986,625.
Although conventional fiber optic connectors are available for satisfactorily terminating low count cables, there are practical considerations which still make these connectors expensive to employ, and expensive to apply, especially where a large number of optical fibers must be terminated in relative small spaces. The individual fiber or low fiber count terminations are also difficult to incorporate in assembly line operations. One option is to incorporate individual fiber optic connectors, ferrules or sleeves into a larger connector bodies and to attach a large number of fibers at once. However, for those applications requiring individual interconnections of two fibers or individual coupling of a single fiber to an active optoelectronic device, precise alignment is still necessary to prevent unacceptable losses.
Although machined multiposition housings can provide such precise alignment, the cost of such machining operations can be prohibitive. For larger scale applications, such as the use of multiposition fiber optic connectors in automobiles, it is especially desirable that lower cost techniques, such as multicavity injection molding be employed. However, the precision attainable with conventional injection molding, is not necessarily compatible with precisely aligned fiber optic interconnection. This is especially true of configurations in which fiber optic ferrules attached to individual optical fibers are positioned in a molded multiposition housing containing a plurality of side by side openings for receiving the ferrules. The stackup of tolerances for multiple side by side openings located in a row is such that the relative spacing of openings at either end may be outside the precise alignment necessary for a suitable low loss optical interconnection. For example, the location of openings in a housing made in one cavity may be significantly different than the location of openings in a housing made in a different cavity.